CVE-2025-27300: ADFO Admin-Form Object Injection Flaw

CVE-2025-27300 Overview

CVE-2025-27300 is a PHP Object Injection vulnerability in the giuliopanda ADFO (admin-form) WordPress plugin. The flaw stems from deserialization of untrusted data [CWE-502] in versions through 1.9.1. An authenticated attacker with high privileges can supply crafted serialized input that the plugin passes to PHP's unserialize() function, instantiating arbitrary PHP objects within the application context.

Critical Impact

Successful exploitation can lead to arbitrary code execution, sensitive data disclosure, and full compromise of the WordPress site through PHP object injection gadget chains.

Affected Products

• giuliopanda ADFO (admin-form) WordPress plugin versions through 1.9.1
• WordPress installations with the ADFO plugin enabled
• Sites granting administrative or equivalent high-privilege access to untrusted users

Discovery Timeline

• 2025-02-24 - CVE-2025-27300 published to NVD
• 2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-27300

Vulnerability Analysis

The ADFO plugin processes serialized PHP data from administrative input without validating the structure or type of objects being instantiated. When PHP's unserialize() function executes on attacker-controlled data, it triggers magic methods such as __wakeup(), __destruct(), and __toString() on reconstructed objects. Attackers chain these magic methods through existing classes loaded by WordPress core, the ADFO plugin, or other active plugins to achieve arbitrary code execution.

The vulnerability requires authentication with high privileges, which limits opportunistic attacks. However, compromised administrator credentials, supply chain compromise, or stacked vulnerabilities can supply the necessary access. The EPSS score of 0.607% reflects current exploitation likelihood given the authentication requirement.

Root Cause

The root cause is unsafe use of PHP deserialization on input that crosses a trust boundary. The plugin treats serialized payloads as structured data rather than executable instructions, ignoring that unserialize() reconstructs object graphs and invokes their lifecycle methods. No allowlist of permitted classes is applied, and no signature or HMAC validates payload integrity before deserialization.

Attack Vector

An authenticated attacker submits a crafted serialized payload to an ADFO endpoint that calls unserialize(). The payload encodes an object graph referencing a known gadget chain in the WordPress codebase. When the plugin deserializes the input, PHP instantiates the objects and invokes their magic methods, triggering the gadget chain. The chain typically terminates in file write, command execution, or sensitive function invocation.

The vulnerability mechanism is described in the Patchstack WordPress Vulnerability Report. No public proof-of-concept code is available.

Detection Methods for CVE-2025-27300

Indicators of Compromise

• Unexpected PHP files written to wp-content/uploads/ or plugin directories with recent modification times
• Outbound network connections from the PHP-FPM or web server process to unfamiliar hosts following ADFO administrative actions
• WordPress audit log entries showing serialized payloads (strings beginning with O: or a:) submitted to ADFO endpoints
• New or modified administrator accounts that do not match change-management records

Detection Strategies

• Inspect HTTP POST bodies sent to ADFO plugin endpoints for PHP serialized object markers such as O:8: or C: followed by class names
• Monitor web server logs for ADFO endpoints generating PHP errors referencing __wakeup, __destruct, or unserialize
• Correlate authenticated administrator sessions with subsequent file system writes outside expected plugin update windows

Monitoring Recommendations

• Enable WordPress activity logging and forward events to a centralized SIEM for correlation with web access logs
• Alert on web shell signatures and unexpected eval(), system(), or passthru() invocations in PHP runtime monitoring
• Track changes to plugin and theme files using file integrity monitoring with cryptographic hashes

How to Mitigate CVE-2025-27300

Immediate Actions Required

• Disable the ADFO plugin until a patched version is confirmed available and installed
• Rotate all WordPress administrator credentials and invalidate active sessions
• Review installed plugins and remove ADFO if it is not business-critical
• Audit recent administrative actions and file system changes for signs of exploitation

Patch Information

At the time of publication, the Patchstack advisory indicates the issue affects ADFO versions through 1.9.1. Administrators should consult the plugin author's repository for any release newer than 1.9.1 and apply updates promptly. If no fixed version is available, removal is the recommended action.

Workarounds

• Restrict access to the WordPress administrative interface using IP allowlisting at the web server or WAF layer
• Enforce multi-factor authentication for all WordPress accounts with administrative privileges
• Deploy a web application firewall rule to block requests containing PHP serialized object patterns destined for ADFO endpoints
• Apply the principle of least privilege and reduce the number of accounts holding administrator-level capabilities

# Example WAF rule (ModSecurity) to block serialized PHP objects in ADFO requests
SecRule REQUEST_URI "@contains /wp-admin/admin.php" \
    "chain,phase:2,deny,status:403,id:1002730001,\
    msg:'Potential PHP object injection targeting ADFO plugin'"
    SecRule ARGS "@rx O:[0-9]+:\"[A-Za-z_\\\\]+\":[0-9]+:" "t:none"